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Progress and Challenges of Semiconducting Materials for Solar Photocatalysis
Published in Inamuddin, Mohd Imran Ahamed, Rajender Boddula, Tariq Altalhi, Optical Properties and Applications of Semiconductors, 2023
Mridula Guin, Tanaya Kundu, Vinay K. Verma, Nakshatra Bahadur Singh
The photocatalytic reactions are dependent on various factors of light, e.g. source, wavelength, intensity etc. In general, the photocatalytic reaction rate escalates with the increase of intensity of the light. Furthermore, the final outcome of the photocatalytic reaction also alters with the light wavelength coming from different sources. TiO2 absorbs the light in the UV region as it has a large band gap of 3.2 eV. The photocatalytic degradation of TiO2 increases with increasing intensity up to 0–20 mW/cm2. However, above the light intensity of about 25 mW/cm2, it is observed that rate of reaction decreases due to the quicker recombination process between electrons and holes (Reza et al. 2015).
Photocatalytic Effect of Tin Oxide-Zinc Oxide Nanocomposites Prepared by the Solvothermal Method
Published in V. R. Remya, H. Akhina, Oluwatobi Samuel Oluwafemi, Nandakumar Kalarikkal, Sabu Thomas, Nanostructured Smart Materials, 2022
Research is going on in these fields, and many of the researchers synthesized nanomaterials, which were used in making solar cells [9], lithium-ion batteries [10] as catalyst [11], as antibacterial and antifungal agents [12], and as sensors [13]. Catalysis is a process where the rate of a chemical transformation of the reactants is modified by a substance without being altered or consumed in the end. The substance used is known as catalyst, and it has the capability to increase the rate of a reaction, thereby reducing the activation energy. Photocatalysis is a process in which light is used to activate the substance, which modifies the rate of a chemical reaction. The substance used to modify the rate of a chemical reaction by irradiating with light is known as photocatalyst.
An Approach for Development of Materials for Green Chemical Catalytic Processes: Green Catalysis
Published in Neha Kanwar Rawat, Iuliana Stoica, A. K. Haghi, Green Polymer Chemistry and Composites, 2021
Rimzhim Gupta, Akanksha Adaval, Sushant Kumar
Photocatalysis drives the chemical reaction by activation of catalysts via absorption of photons.84 Photocatalysts are the substances that facilitate the active surface sites for pollutants or reactant molecules to adsorb/adhere at its surface. The photocatalysts are the photoactive materials/semiconductors that absorb in UV/visible or infrared wavelengths. Absorption of photons of energy equal to its bandgap facilitates the excitation of electrons from valence band to the empty conduction band, leaving behind a vacancy of opposite charge, that is, holes. These bands are the filled or unfilled orbitals of the elements of the respective semiconductor. Based on the location of maxima of valence and minima of the conduction band, band gaps are classified into two categories, that is, direct and indirect band gaps. The species adsorbed at the surface of catalysts are hydroxyl ion and dissolved oxygen.85 The following schematic shows the photon absorption, recombination, and surface reactions in a semiconductor (Fig. 8.8).
A facile approach to develop multifunctional cotton fabrics with hydrophobic, self-cleaning and UV protection properties using ZnO particles and fluorocarbon
Published in The Journal of The Textile Institute, 2022
Yuanfeng Wang, Vijay Baheti, Muhammad Zaman Khan, Martina Viková, Kai Yang, Tao Yang, Jiří Militký
Another self-cleaning effect is based on the photocatalytic mechanism of inorganic materials (Afzal et al., 2014; Tung & Daoud, 2011). Organic stains on a photocatalytic coated surface can be chemically degraded to CO2 and H2O under UV light due to the photocatalytic reaction, which is a clean process without high temperature, high energy consumption, and waste residue (Yang et al., 2019). The most commonly used photocatalytic inorganic materials are zinc oxide (ZnO) and titanium dioxide (TiO2). TiO2 is efficient for photocatalytic degradation of stains due to a faster transfer of electron to molecular oxygen (Panwar et al., 2018). However, high-cost water treatment processes limit the large-scale application of TiO2 on textile industry (Daneshvar et al., 2004). In this context, ZnO, with a direct wide band gap (3.37 eV) and large exciton binding energy (60 meV), was found to be a suitable alternative of TiO2 due to its similar photodegradation ability to the TiO2. Recently, numerous studies have focus on fabricating photocatalytic and hydrophobic surface simultaneously, meaning that the surface can not only repel water, but also resist organic stains. However, the development of this multifunctional textile surface is still a challenge as either the inadequate photocatalysis show on a superhydrophobic surface or superhydrophobicity losses under solar irradiation (Xu et al., 2015).
Hydrothermal assembly, structural diversity, and photocatalytic characterization of two polyoxometalates-based hybrid CuII and CuI coordination polymers with 2,6-(1,2,4-triazole-4-yl)pyridine
Published in Inorganic and Nano-Metal Chemistry, 2021
Yuan-Yuan Liu, Jun-Dan An, Tian-Tian Wang, Yong Li, Bin Ding
Photocatalysis has the advantages of simple operation, low energy consumption, no secondary pollution, and high efficiency. Photocatalytic purification technology has the advantages of deep oxygen at room temperature, low secondary pollution, low operating cost, and the hope of using sunlight as a reaction light source. Therefore, photocatalysis is particularly suitable for the purification of indoor volatile organic compounds, which shows huge applications in deep purification potential. Common photocatalysts are mostly metal oxides and sulfides, such as TiO2, ZnO, CdS, WO3, etc. Among them, TiO2 has the best comprehensive performance and the most widely used.[45] At the same time, we learned the POMs are a broad class of metal oxide clusters, characterized by a negatively charged macromolecular structure, with interesting acids/bases, redox and photochemical properties. Therefore the development of POM-based CuII and CuI hybrid compounds in this work can produce new multifunctional materials with good photo-catalytic properties.[46,47]
Photocatalytic degradation of organic pollutants in wastewater by heteropolyacids: a review
Published in Journal of Coordination Chemistry, 2021
Zhang Chengli, Ma Ronghua, We Qi, Yang Mingrui, Cao Rui, Zong Xiaonan
Most semiconductors used for photocatalysis are metal oxides, such as TiO2, ZnO, SnO2, etc. With TiO2 having higher photocatalytic activity, It has the characteristics of acid and alkali resistance, low cost, and non-toxic. But pure TiO2 also has many shortcomings. For example, the utilization rate of solar energy is low. The band gap of TiO2 is 3.2 eV, which can only absorb a very small part of the wavelength of sunlight. As a photosensitive substance, heteropolyacid can enhance the photo-oxidation activity in water and some organic solvents at room temperature after being combined with other substances, and has constant light absorption efficiency in ultraviolet and visible light regions. Loading heteropolyacid on TiO2 can make the two form a synergistic effect and improve the photocatalytic activity of the material [54].